This application is based upon and claims the benefit of priority from prior Japanese Patent Application 2001-262294 filed on Aug. 30, 2001; the entire contents of which are incorporated by reference herein.
1. Field of the Invention
The present invention relates to dry cleaning using a halogen gas for a manufacturing apparatus. In particular, it relates to a system determining timing to perform dry cleaning for the manufacturing apparatus, a method for reducing damage to the manufacturing apparatus in performing dry cleaning, and a method for efficiently controlling the dry cleaning.
2. Description of the Related Art
In a chemical vapor deposition (CVD) apparatus for semiconductor manufacturing, especially in a low pressure CVD (LPCVD) apparatus, a film such as a silicon oxide (SiO2) film accumulates on a wall of a CVD chamber. When an accumulated deposition film grows too thick, problems may occur, such as a dust contamination caused by the peeling of the deposition film, and also a lack of uniformity in a film thickness deposited on a semiconductor wafer caused by a non-homogeneous deposition in the CVD chamber. Conventionally, before these problems come to the forefront, a dry cleaning by a cleaning gas including a halogen such as a chlorine trifluoride (ClF3) gas is used to remove the accumulation of the deposition film in the CVD chamber.
Typically, the dry cleaning is carried out when conditions develop where normal processing with required quality becomes difficult, such as the dust contamination occurs because of the peeling of the film due to excess thickness of the accumulation of the deposition film in the CVD chamber, or deterioration of the uniformity of the film thickness on top of the wafer develops due to non-homogeneous deposition. In addition, through experience, it is possible to understand when the excessive accumulation conditions will occur, and being subject to these problems, a cleaning schedule may be determined.
In addition, in the LPCVD apparatus, for example, upon arrival of a lot for a corresponding process, a target film thickness for the film deposition and respective accumulated deposition thicknesses in a single or a plurality of apparatuses are speculated. Thereafter, the LPCVD apparatus is determined the timing of cleaning and selected for the film deposition from the apparatuses wherein a specific film thickness is not exceeded. These selections all depend on manual decision.
Similarly, when performing cleaning, determination whether or not to perform cleaning on the LPCVD apparatus is made through manual decision based on the determination of those apparatuses where accumulated deposition thickness exceeds a preset value or film deposition thickness of a lot scheduled for processing. Thus, conventionally, for a single or a plurality of apparatuses, manual decision is used to decide whether to implement film deposition or implement cleaning based solely on the accumulated deposition thickness in each apparatus.
In addition, when performing cleaning, especially using the ClF3 gas, the CVD chamber is set to conditions of a certain temperature and pressure, and the ClF3 gas in addition to an inert gas, such as nitrogen (N2) are fed into the CVD chamber in order to remove the deposited film. When removing the deposited film, an active gas such as ClF3 is merely mixed with an inert gas such as N2. No countermeasure is taken for reducing the cleaning time by increasing an etching rate, and for improving selectivity between the deposited film and the CVD chamber components. In addition, cleaning time is determined to be sufficient through experience in view of the accumulated film type and the accumulated deposition thickness. However, since an end point is not actually known, the cleaning is applied for a longer time than necessary, and damage to the components due to this excessive time is not considered.
Thus, in the conventional LPCVD apparatus, for example, a cleaning schedule is determined solely by the problems associated with the film deposition performance, and the damage to the CVD chamber components due to cleaning is not considered. Therefore, there are disadvantages such as increased frequency of apparatus component maintenance, increased load on the operator, and increased cost of ownership (COO).
In either case of depositing a film or performing cleaning, a person determines which of a single or a plurality of apparatuses should be used based solely on the accumulated deposition thickness value in each of the apparatus. Therefore, since efficient determination cannot be performed in a short time based on information such as a production flow condition of the multiple lots, a post-process apparatus condition, an operation of incidental facilities, a maintenance prediction, and an accumulated deposition thickness of the apparatus, inconveniences such as delay of the lot processing may occur.
In addition, the conventional method using a pure ClF3 gas does not improve the etching rate and selectivity. Moreover, performing processing for a sufficient length of time without knowing the cleaning end point invites enormous time and costs for the cleaning process itself, in addition to gas dissipation. In addition, since cleaning is performed for a time duration in excessive of the optimum duration, damage to the CVD chamber components increases.
In addition, for example etching gas such as a ClF3 is used in a dry cleaning method for the deposited film inside the LPCVD apparatus. Typically, in the LPCVD process, not only is the target film adhered to the inside wall of the CVD chamber in the LPCVD apparatus, but by-products may also agglutinate on portions from an exhaust piping to a vacuum pump. Therefore, with the cleaning, it is better that cleaning removal be possible for not only the deposited film on the wall of the CVD chamber but also by-products. Nevertheless, currently, the cleaning is not performed for the exhaust piping and the vacuum pump since determination of the cleaning end point is not clear.
In addition, since the cleaning rate at higher temperature is faster, cleaning is performed under heated conditions. However, in order to avoid simultaneous damage to the CVD chamber components, the temperature cannot be raised excessively. As the result, the cleaning process is performed under conditions allowing a certain degree of selectivity to be obtained between the deposited film and the CVD chamber components and giving a tolerable cleaning rate for the deposited film. The cleaning time is set to be sufficiently long as required. Therefore, since the cleaning ends quickly at locations in the upstream of the etching gas flow, an over-etching time is longer in the upstream and may make it easier for problems to occur such as damage to the CVD chamber components.
A first aspect of the present invention inheres in a system for determining dry cleaning timing, including: a manufacturing apparatus configured to process materials assigned by a sequence of lots; an apparatus controller configured to control the manufacturing apparatus and obtaining operational conditions of the manufacturing apparatus as apparatus information; a lot information input terminal configured to obtain process conditions of one of the lots as lot information; an apparatus information storage unit configured to store the apparatus information from the apparatus controller as an apparatus information database; a lot information storage unit configured to store the lot information from the lot information input terminal as a lot information database; and a cleaning determination unit configured to determine timing to perform a dry cleaning of the manufacturing apparatus based on the apparatus information database and the lot information database.
A second aspect of the present invention inheres in a method for determining dry cleaning timing, including: obtaining operational conditions of a manufacturing apparatus as apparatus information; obtaining process conditions of one of lots processed in the manufacturing apparatus as lot information; and determining timing to perform a dry cleaning for the manufacturing apparatus based on the apparatus information and the lot information.
A third aspect of the present invention inheres in a dry cleaning method including: depositing a film in a manufacturing apparatus; obtaining operational conditions of the manufacturing apparatus as apparatus information; obtaining process conditions of one of lots to be processed in the manufacturing apparatus as lot information; determining timing to perform a dry cleaning for the manufacturing apparatus based on the apparatus information and the lot information; and performing the dry cleaning with a cleaning gas including a halogen gas.
A fourth aspect of the present invention inheres in a method for manufacturing a semiconductor device, including: depositing a film in a manufacturing apparatus; obtaining operational conditions of the manufacturing apparatus as apparatus information; obtaining process conditions of one of lots to be processed in the manufacturing apparatus as lot information; determining timing to perform a dry cleaning for the manufacturing apparatus based on the apparatus information and the lot information; performing the dry cleaning with a cleaning gas including a halogen gas; loading semiconductor wafers assigned as the one of the lots in a chamber of the manufacturing apparatus; and performing a film deposition on the semiconductor wafers.